1. Technical Field
This application generally relates to a method and system for processing a digital image and, more particularly, for processing a digital image comprising a document image and surrounding image.
2. Description of Related Art
Document management systems are becoming increasingly popular. Such systems ease the burden of storing and handling large databases of documents. To use such systems with paper documents, digital images of the paper documents to be electronically stored must be captured.
There are a variety of potential devices for capturing digital images of paper documents, including digital cameras, scanners, and cellular phones with built-in digital cameras. Digital images of documents may also be obtained by digitizing an image of a document captured with a conventional film camera. A variety of systems also exist for processing digital images of paper documents captured by such devices. For example, it is known to separate the document image in a captured image from the remainder or surrounding image using a process known as segmentation.
Although segmentation processes may be applicable to both camera and scanner captured images, it tends to be easier to separate the imaged document from the surrounding image in scanner captured images than camera captured images. This is because the conditions under which the image is captured tend to vary more when using a camera than a scanner. It is also more likely that conditions that are less than optimal for existing segmentation techniques—including shadows, poor lighting, indistinct backgrounds, multiple documents in image, and occlusions due to folds, paperclips, tears, etc.—will be encountered when using a camera to capture an image of a document. Use of a camera can also introduce image distortions, which are generally less prevalent in scanner captured images. Such distortions may include distortions caused by the angle of the camera relative to the document (“perspective distortion”), the lens used by the camera and its distance from the document, the relative flatness of the document (e.g., whether the document being imaged is situated on a flat or curved surface), and other factors. As a result, currently known segmentation techniques do not adequately segment the captured image in many situations, particularly when the captured image has been captured using a camera. A need, therefore, exists for an improved system and method for segmenting a captured digital image of a document into an imaged document and its surrounding image. More particularly, a need exists for a system and method of segmenting that provides improved segmentation rates when one or more of the less than optimal conditions mentioned above are encountered.